Synthetic polymers are often prepared by employing metal-containing initiators, catalysts, and co-catalysts. The quantity or level of metal employed, however, is often small and therefore the residue of these metal compounds often remains within the resulting polymeric composition.
In certain applications, however, the presence of even small amounts of metal compounds may not be desirable. This may be particularly true where the appearance or optical properties of the polymer are critical to their use. For example, it may be desirable for the polymer to be clear and deflect a minimum amount of light. For example, where polymeric compositions are employed in the manufacture of food containers, such as bottles, it is often desirable for the container to exhibit clarity so that the food or beverage can be readily viewed.
In certain situations, however, the presence of small amounts of metal compounds, as well as certain organic compounds, may have a deleterious impact on this clarity. In particular, certain metal compounds may deflect or absorb light and thereby result in polymeric compositions that appear hazy, cloudy, or possess undesirable color. Likewise, in electronic applications, it may be desirable for polymers employed therein to be free of or include less than appreciable amounts of metal.
There is therefore a need to provide a method for reducing the quantity of metal found within many synthetic polymers. For example, there is a need to reduce the amount of lithium located in low molecular weight, anionically polymerized polymers, which include higher amounts of metal due to the fact that the amount of metal employed in polymerization is inversely related to the molecular weight of the polymer synthesized.